The invention relates to water heaters, and more particularly to direct contact water heaters.
Direct contact water heaters, such as those disclosed in U.S. Pat. Nos. 4,275,708 and 4,574,775 generally comprise a vertically oriented cylindrical column having a plurality of heat exchange bodies disposed adjacent its upper end. A spray nozzle is disposed in the upper end of the column for spraying the water to be heated downwardly onto the heat exchange bodies. A gas burner extends through an opening in the column and below the heat exchange bodies for injecting a flame radially inwardly toward the axis of the column. The hot gasses from the flame pass upwardly in counter-flow to the water to be heated, which flows downwardly and around the heat exchange bodies.
In the water heater disclosed in U.S. Pat. No. 4,275,708, the burner flame was directed inwardly toward a plate at the opposite side of the column for directing gasses upwardly and away from the wall of the combustion chamber. This configuration resulted in incomplete combustion, which lowers efficiency and causes high levels of carbon monoxide (CO) in the discharge gasses. In addition, a local hot spot was produced on the gas diversion plate, causing higher than acceptable levels of nitrogen oxide (NOx). These deficiencies were alleviated to some extend by the water heater disclosed in U.S. Pat. No. 4,574,775 wherein the heated gasses were injected tangentially into the combustion chamber, thereby increasing efficiency and decreasing levels of carbon monoxide and nitrogen oxide in the discharge gasses. However, this tangential method of firing also caused hot spots in the vicinity of the burner which resulted in levels of NOx which exceeded permissible limits in certain locations.